/*
 * MIT License
 *
 * Copyright (c) 2023 北京凯特伟业科技有限公司
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */
package com.je.bpm.common.el;

import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.node.ObjectNode;
import javax.el.*;
import java.beans.FeatureDescriptor;
import java.math.BigDecimal;
import java.util.Iterator;
import java.util.List;

/**
 * Defines property resolution behavior on JsonNodes.
 *
 * @see CompositeELResolver
 * @see ELResolver
 */
public class JsonNodeELResolver extends ELResolver {

    private final boolean readOnly;
    private final ObjectMapper defaultObjectMapper = new ObjectMapper();

    /**
     * Creates a new read/write BeanELResolver.
     */
    public JsonNodeELResolver() {
        this(false);
    }

    /**
     * Creates a new BeanELResolver whose read-only status is determined by the
     * given parameter.
     */
    public JsonNodeELResolver(boolean readOnly) {
        this.readOnly = readOnly;
    }

    /**
     * If the base object is not null, returns the most general type that this
     * resolver accepts for the property argument. Otherwise, returns null.
     * Assuming the base is not null, this method will always return
     * Object.class. This is because any object is accepted as a key and is
     * coerced into a string.
     *
     * @param context The context of this evaluation.
     * @param base    The bean to analyze.
     * @return null if base is null; otherwise Object.class.
     */
    @Override
    public Class<?> getCommonPropertyType(ELContext context, Object base) {
        return isResolvable(base) ? Object.class : null;
    }

    /**
     * If the base object is not null, returns an Iterator containing the set of
     * JavaBeans properties available on the given object. Otherwise, returns
     * null. The Iterator returned must contain zero or more instances of
     * java.beans.FeatureDescriptor. Each info object contains information about
     * a property in the bean, as obtained by calling the
     * BeanInfo.getPropertyDescriptors method. The FeatureDescriptor is
     * initialized using the same fields as are present in the
     * PropertyDescriptor, with the additional required named attributes "type"
     * and "resolvableAtDesignTime" set as follows:
     * <ul>
     * <li>{@link ELResolver#TYPE} - The runtime type of the property, from
     * PropertyDescriptor.getPropertyType().</li>
     * <li>{@link ELResolver#RESOLVABLE_AT_DESIGN_TIME} - true.</li>
     * </ul>
     *
     * @param context The context of this evaluation.
     * @param base    The bean to analyze.
     * @return An Iterator containing zero or more FeatureDescriptor objects,
     * each representing a property on this bean, or null if the base
     * object is null.
     */
    @Override
    public Iterator<FeatureDescriptor> getFeatureDescriptors(ELContext context, Object base) {
        if (isResolvable(base)) {
            JsonNode node = (JsonNode) base;
            final Iterator<String> keys = node.fieldNames();
            return new Iterator<FeatureDescriptor>() {
                @Override
                public boolean hasNext() {
                    return keys.hasNext();
                }

                @Override
                public FeatureDescriptor next() {
                    Object key = keys.next();
                    FeatureDescriptor feature = new FeatureDescriptor();
                    feature.setDisplayName(key == null ? "null" : key.toString());
                    feature.setName(feature.getDisplayName());
                    feature.setShortDescription("");
                    feature.setExpert(true);
                    feature.setHidden(false);
                    feature.setPreferred(true);
                    feature.setValue(ELResolver.TYPE, key == null ? "null" : key.getClass());
                    feature.setValue(ELResolver.RESOLVABLE_AT_DESIGN_TIME, true);
                    return feature;

                }

                @Override
                public void remove() {
                    throw new UnsupportedOperationException("cannot remove");
                }
            };
        }
        return null;
    }

    /**
     * If the base object is a map, returns the most general acceptable type for
     * a value in this map. If the base is a Map, the propertyResolved property
     * of the ELContext object must be set to true by this resolver, before
     * returning. If this property is not true after this method is called, the
     * caller should ignore the return value. Assuming the base is a Map, this
     * method will always return Object.class. This is because Maps accept any
     * object as the value for a given key.
     *
     * @param context  The context of this evaluation.
     * @param base     The map to analyze. Only bases of type Map are handled by this
     *                 resolver.
     * @param property The key to return the acceptable type for. Ignored by this
     *                 resolver.
     * @return If the propertyResolved property of ELContext was set to true,
     * then the most general acceptable type; otherwise undefined.
     * @throws NullPointerException if context is null
     * @throws ELException          if an exception was thrown while performing the property or
     *                              variable resolution. The thrown exception must be included as
     *                              the cause property of this exception, if available.
     */
    @Override
    public Class<?> getType(ELContext context, Object base, Object property) {
        if (context == null) {
            throw new NullPointerException("context is null");
        }
        Class<?> result = null;
        if (isResolvable(base)) {
            result = Object.class;
            context.setPropertyResolved(true);
        }
        return result;
    }

    /**
     * If the base object is a map, returns the value associated with the given
     * key, as specified by the property argument. If the key was not found,
     * null is returned. If the base is a Map, the propertyResolved property of
     * the ELContext object must be set to true by this resolver, before
     * returning. If this property is not true after this method is called, the
     * caller should ignore the return value. Just as in
     * java.util.Map.get(Object), just because null is returned doesn't mean
     * there is no mapping for the key; it's also possible that the Map
     * explicitly maps the key to null.
     *
     * @param context  The context of this evaluation.
     * @param base     The map to analyze. Only bases of type Map are handled by this
     *                 resolver.
     * @param property The key to return the acceptable type for. Ignored by this
     *                 resolver.
     * @return If the propertyResolved property of ELContext was set to true,
     * then the value associated with the given key or null if the key
     * was not found. Otherwise, undefined.
     * @throws ClassCastException   if the key is of an inappropriate type for this map
     *                              (optionally thrown by the underlying Map).
     * @throws NullPointerException if context is null, or if the key is null and this map does
     *                              not permit null keys (the latter is optionally thrown by the
     *                              underlying Map).
     * @throws ELException          if an exception was thrown while performing the property or
     *                              variable resolution. The thrown exception must be included as
     *                              the cause property of this exception, if available.
     */
    @Override
    public Object getValue(ELContext context, Object base, Object property) {
        if (context == null) {
            throw new NullPointerException("context is null");
        }
        Object result = null;
        if (isResolvable(base)) {
            JsonNode resultNode = ((JsonNode) base).get(property.toString());
            if (resultNode != null && resultNode.isValueNode()) {
                if (resultNode.isBoolean()) {
                    result = resultNode.asBoolean();
                } else if (resultNode.isLong()) {
                    result = resultNode.asLong();
                } else if (resultNode.isBigDecimal() || resultNode.isDouble()) {
                    result = resultNode.asDouble();
                } else if (resultNode.isTextual()) {
                    result = resultNode.asText();
                } else {
                    result = resultNode.toString();
                }

            } else {
                if (resultNode.isArray()) {
                    result = getObjectMapper().convertValue(resultNode, List.class);
                } else {
                    result = resultNode;
                }
            }
            context.setPropertyResolved(true);
        }
        return result;
    }

    /**
     * Returns the {@link ObjectMapper} used internally to convert {@link List}
     * properties. Subclasses may override this method to provide a specific one
     */
    protected ObjectMapper getObjectMapper() {
        return defaultObjectMapper;
    }

    /**
     * If the base object is a map, returns whether a call to
     * {@link #setValue(ELContext, Object, Object, Object)} will always fail. If
     * the base is a Map, the propertyResolved property of the ELContext object
     * must be set to true by this resolver, before returning. If this property
     * is not true after this method is called, the caller should ignore the
     * return value. If this resolver was constructed in read-only mode, this
     * method will always return true. If a Map was created using
     * java.util.Collections.unmodifiableMap(Map), this method must return true.
     * Unfortunately, there is no Collections API method to detect this.
     * However, an implementation can create a prototype unmodifiable Map and
     * query its runtime type to see if it matches the runtime type of the base
     * object as a workaround.
     *
     * @param context  The context of this evaluation.
     * @param base     The map to analyze. Only bases of type Map are handled by this
     *                 resolver.
     * @param property The key to return the acceptable type for. Ignored by this
     *                 resolver.
     * @return If the propertyResolved property of ELContext was set to true,
     * then true if calling the setValue method will always fail or
     * false if it is possible that such a call may succeed; otherwise
     * undefined.
     * @throws NullPointerException if context is null.
     * @throws ELException          if an exception was thrown while performing the property or
     *                              variable resolution. The thrown exception must be included as
     *                              the cause property of this exception, if available.
     */
    @Override
    public boolean isReadOnly(ELContext context, Object base, Object property) {
        if (context == null) {
            throw new NullPointerException("context is null");
        }
        if (isResolvable(base)) {
            context.setPropertyResolved(true);
        }
        return readOnly;
    }

    /**
     * If the base object is a map, attempts to set the value associated with
     * the given key, as specified by the property argument. If the base is a
     * Map, the propertyResolved property of the ELContext object must be set to
     * true by this resolver, before returning. If this property is not true
     * after this method is called, the caller can safely assume no value was
     * set. If this resolver was constructed in read-only mode, this method will
     * always throw PropertyNotWritableException. If a Map was created using
     * java.util.Collections.unmodifiableMap(Map), this method must throw
     * PropertyNotWritableException. Unfortunately, there is no Collections API
     * method to detect this. However, an implementation can create a prototype
     * unmodifiable Map and query its runtime type to see if it matches the
     * runtime type of the base object as a workaround.
     *
     * @param context  The context of this evaluation.
     * @param base     The map to analyze. Only bases of type Map are handled by this
     *                 resolver.
     * @param property The key to return the acceptable type for. Ignored by this
     *                 resolver.
     * @param value    The value to be associated with the specified key.
     * @throws ClassCastException           if the class of the specified key or value prevents it from
     *                                      being stored in this map.
     * @throws NullPointerException         if context is null, or if this map does not permit null keys
     *                                      or values, and the specified key or value is null.
     * @throws IllegalArgumentException     if some aspect of this key or value prevents it from being
     *                                      stored in this map.
     * @throws PropertyNotWritableException if this resolver was constructed in read-only mode, or if the
     *                                      put operation is not supported by the underlying map.
     * @throws ELException                  if an exception was thrown while performing the property or
     *                                      variable resolution. The thrown exception must be included as
     *                                      the cause property of this exception, if available.
     */
    @Override
    public void setValue(ELContext context, Object base, Object property, Object value) {
        if (context == null) {
            throw new NullPointerException("context is null");
        }
        if (base instanceof ObjectNode) {
            if (readOnly) {
                throw new PropertyNotWritableException("resolver is read-only");
            }
            ObjectNode node = (ObjectNode) base;
            if (value instanceof BigDecimal) {
                node.put(property.toString(), (BigDecimal) value);

            } else if (value instanceof Boolean) {
                node.put(property.toString(), (Boolean) value);

            } else if (value instanceof Long) {
                node.put(property.toString(), (Long) value);

            } else if (value instanceof Double) {
                node.put(property.toString(), (Double) value);

            } else if (value != null) {
                node.put(property.toString(), value.toString());

            } else {
                node.putNull(property.toString());
            }
            context.setPropertyResolved(true);
        }
    }

    /**
     * Test whether the given base should be resolved by this ELResolver.
     */
    private final boolean isResolvable(Object base) {
        return base instanceof JsonNode;
    }
}
